Emergence,maturation and upstream oviposition flights of Plecoptera from the Breitenbach,with notes on the adult phase as a possible control of stream insect populations |
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Authors: | Peter Zwick |
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Institution: | 1. Limnologische Flu?station Schlitz des Max-Planck-Instituts für Limnologie, Postfach 260, D 6407, Schlitz, Federal Republic of Germany
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Abstract: | Upstream oviposition flights of several Plecoptera species of the genera Leuctra, Nemoura, Isoperla and Siphonoperla along the Breitenbach, Hesse, Germany are inferred from 1. oviposition occuring upstream from emergence areas; 2. size differences
and size-shifts between emerging and egg-laying females; 3. concentration of oviposition in upstream sections of the emergence
area. The last point relies on direct catches of egg-laying females with sticky traps, and on over-representation of old,
mature females in upstream emergence traps towards the end of, or even after actual emergence periods. Criteria for age class
discrimination of the respective taxa are described. The validity of the present and of other indirect evidence for directed
adult flights and the significance of adult upstream displacement are discussed. Optical orientation cues are suggested.
Females of Leuctra prima and Siphonoperla torrentium are shown to gain 25–50% dry weight by feeding in the terrestrial environment; general information indicates many other Plecoptera
may be similar in this respect. Terrestrial adult life is shown to last for 3–8 weeks. This long time, evidence of important
flight activity and feeding together suggest that the terrestrial phase is spent as an active adult, the inevitable risks
of which may form an important control of population dynamics. |
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Keywords: | Plecoptera terrestrial adults oviposition colonisation cycle upstream flights population control |
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